Have you set your Preferences? Photoshop preferences will allow you to customize Photoshop to your designing style, while helping to utilize your available computer resources that can increase your overall performance.

As far as the background color of the work space, on PC you can also just right click on it at anytime and a window will open for you to choose among several of the default colors - various shades of gray - or even a custom color. I tend to want to change my background work space color depending on what I'm working on and what sort of contrast I need to better see. Sometimes a lighter color is better, other times dark.

When I select "File -New" on CS2, the file always defaults to custom size. I have created a 12X12 file, but I don't know how to set it as my default. It would save me loads of time if I didn't have to continually choose 12X12.